The use of thermal energy for sealing blood vessels and reducing hemorrhage (hemostasis) in surgery is well known. Various heating means separate from the means used to cut the blood vessels are used during surgery to achieve the hemostasis effect, e.g., auxiliary heating devices as well as lasers. In laser surgery, both argon lasers and carbon dioxide lasers have been used as scalpels for tissue coagulation and hemostasis. The laser scalpels are expensive and bulky, requiring large power supplies and a complex system of heavy mirrors. This makes them inconvenient and cumbersome to use.
Also known are steel blades which are similar to conventional scalpels except that adhered thereto via an adhesive layer is a printed circuit heating element mounted on a polyimide foil. However, the performance of such steel blades is severely limited. The adhesive layer, the polyimide foil thickness and the body of the steel blade severely limit heat transmission from the heating element to the cutting edge of the blade. To achieve a desired amount of heat transmission at the cutting edge of the blades, the temperature of the heating element must be raised to a very high temperature to allow for the loss in heat transmission from the heating element to the cutting edge. However, since the temperature of the heating element must be raised almost 100.degree. C. above the required temperature of the cutting edge to achieve the desired amount of heat transmission at the cutting edge of the blade, the proximity of the heated non-cutting portions of the blade will burn tissue adjacent to the heating element rather than coagulating blood vessels at the cutting edge. Furthermore, the steel cutting edge of the blade will corrode rapidly upon contact with body fluids at such elevated temperatures.
U.S. Pat. No. 3,826,263 to Cage et al. describes a ceramic scalpel blade with a resistance heater emplaced at the cutting edge. The material of the heater preferably has a negative temperature coefficient of resistance. U.S. Pat. No. 3,768,482 to Shaw describes a ceramic blade having a plurality of electrical heating elements disposed on the cutting edges of the blade. Ceramic blades such as those described by Cage et al. and Shaw have not been practical. The ceramic body of the blade was found to be too brittle and thermally non-conductive for practical use. In addition, the heating element(s) was crammed into a very confined area, rendering heating ineffective and making temperature control difficult.
U.S. Pat. No. 4,534,347 to Taylor describes a microwave energy heated scalpel in which the blade is not heated directly. The blade consists of a conducting open loop, and in operation, microwave energy is emitted from the scalpel and absorbed in the tissue being surgically cut to a depth of approximately 10 mm, causing coagulation of blood vessels.